Respiring biological materials consume oxygen (O2) and produce carbon dioxide (CO2) at rates which depend upon temperature and the stage of their development. Ideally, a respiring material should be stored in a container whose permeability to O2 and CO2 is correlated with (i) the atmosphere outside the package, (ii) the rates at which the material consumes O2 and produces CO2, and (iii) the temperature, to produce the desired atmosphere within the container. This is the principle behind the technology of modified atmosphere packaging (MAP), as discussed, for example, in U.S. Pat. No. 3,450,542 (Badran), U.S. Pat. No. 3,450,544 (Badran et al.), U.S. Pat. No. 3,798,333 (Cummin et al. U.S. Pat. No. 4,734,324 (Hill), U.S. Pat. No. 4,830,863 (Jones), U.S. Pat. No. 4,842,875 (Anderson), U.S. Pat. No. 4,879,078 (Antoon), U.S. Pat. No. 4,910,032 (Antoon), U.S. Pat. No. 4,923,703 (Antoon), U.S. Pat. No. 5,045,331 (Antoon), U.S. Pat. No. 5,160,768 (Antoon), U.S. Pat. No. 5,254,354 (Stewart), U.S. Pat. No. 6,013,293 (De Moor), U.S. Pat. No. 6,376,032 (Clarke) and U.S. Pat. No. 6,548,132 (Clarke), International Publication Numbers WO 94/12040 (Fresh Western), WO 96/38495 (Landec) and WO 00/04787 (Landec), and European Patent Applications Nos. 0,351,115 and 0,351,116 (Courtaulds). The disclosure of each of these patents, applications and publications is incorporated herein by reference.
Bananas are respiring biological materials whose storage and ripening present the most serious problems because                (i) bananas are grown in locations far distant from the locations at which they are consumed;        (ii) they are damaged by storage at temperatures below about 14.4° C., with the extent of the damage depending upon the time spent below that temperature and how far the temperature is below 14.4° C. (58° F.);        (iii) they go through a climacteric when they ripen, thus producing a very large increase in respiration rate and the generation of heat;        (iv) they generate ethylene as they ripen, and they ripen at a rate which increases with the concentration of ethylene around them—as a result, a single prematurely ripe banana can trigger premature ripening of many others; and        (iv) once they have ripened, and have been exposed to air, they rapidly become over-ripe.These problems have not yet been solved. The conventional procedure is to harvest the bananas when they are hard, green and unripe; to transport the green bananas, at 13-14° C., to the location where they will be consumed; to ripen the green bananas by exposing them to ethylene in a ripening room at that location; and to place the ripened bananas on sale. The time at which the bananas are harvested depends on the time needed to transport them to the point-of-sale. Thus bananas are typically harvested at week 11 (i.e. 11 weeks after the flower emerges from the plant) or week 12. The green bananas are shipped in bags made of polyethylene about 0.04 to 0.06 mm (1.5-2.5 mil) thick, with each bag containing about 18 kg (40 lb) of bananas and being supported by a cardboard box. In many cases, after the bananas have been placed in the bag, most of the air is exhausted from the bag, and the bag is then sealed; this is the procedure generally described in U.S. Pat. No. 3,450,542 (Badran). In other cases, the bag contains vent holes.        
A serious disadvantage of the conventional procedure is the need to harvest the bananas a good while before they are fully grown. It would be desirable to harvest the bananas at a later time, when they are larger. However, the later the bananas are picked, the greater the propensity for their climacteric to be triggered by small concentrations of ethylene, and experience has shown that if the bananas are harvested later than the presently established timetables, this results in prematurely ripe bananas when the bananas are shipped in vented bags, and in so-called “green-ripe” bananas when the bananas are shipped in sealed bags. Green-ripe bananas soften, but remain green, and have an unpleasant flavor.
Another serious disadvantage of the conventional procedure is that, in order to ripen the green bananas by exposing them to ethylene, it is necessary to open each of the shipping bags if, as in most cases, the bags have been sealed during shipping.
Another serious disadvantage of the conventional procedure is that the bananas, once ripened, must be sold within a few days, or scrapped.
Another serious disadvantage of the conventional procedure is that the heat generated by the ripening of the bananas is generated over a relatively short period of time, which heats the bananas to an extent that causes dehydration of the bananas and/or increases the demand on the refrigeration equipment used to keep the bananas cool.